[Bug]: Go Prism Runner Concurrent Map Mutations

### What happened?

There are race conditions in the Server of the prism runner's gRPC server in Go. Reads and writes to the [`artifacts` variable within Server](https://github.com/apache/beam/blob/d84cfffd017342542cc1dc3e7ae30452a485e3b1/sdks/go/pkg/beam/runners/prism/internal/jobservices/server.go#L61C2-L61C10) are not protected by a mutex. This means race detection will occasionally crash this logic because it's not thread safe.

Given the nature of this class. It's likely other variables are at risk of races as well.

```
fatal error: concurrent map writes

goroutine 1737 [running]:
github.com/apache/beam/sdks/v2/go/pkg/beam/runners/prism/internal/jobservices.(*Server).ReverseArtifactRetrievalService(0xc0001195c0, {0x29c74a0, 0xc000be4570})
/github/home/go/pkg/mod/github.com/apache/beam/sdks/v2@v2.59.0/go/pkg/beam/runners/prism/internal/jobservices/artifact.go:87 +0x885
github.com/apache/beam/sdks/v2/go/pkg/beam/model/jobmanagement_v1._ArtifactStagingService_ReverseArtifactRetrievalService_Handler({0x2693b80?, 0xc0001195c0}, {0x29c06d0, 0xc000b321e0})
/github/home/go/pkg/mod/github.com/apache/beam/sdks/v2@v2.59.0/go/pkg/beam/model/jobmanagement_v1/beam_artifact_api_grpc.pb.go:272 +0xd8
google.golang.org/grpc.(*Server).processStreamingRPC(0xc000565a00, {0x29bb248, 0xc000b138c0}, {0x29d4640, 0xc000494b60}, 0xc00167a7e0, 0xc000319c80, 0x4ced6a0, 0x0)
/github/home/go/pkg/mod/google.golang.org/grpc@v1.67.1/server.go:1688 +0x1208
google.golang.org/grpc.(*Server).handleStream(0xc000565a00, {0x29d4640, 0xc000494b60}, 0xc00167a7e0)
/github/home/go/pkg/mod/google.golang.org/grpc@v1.67.1/server.go:1809 +0xe3a
google.golang.org/grpc.(*Server).serveStreams.func2.1()
/github/home/go/pkg/mod/google.golang.org/grpc@v1.67.1/server.go:1029 +0x7f
created by google.golang.org/grpc.(*Server).serveStreams.func2 in goroutine 1616
/github/home/go/pkg/mod/google.golang.org/grpc@v1.67.1/server.go:1040 +0x125
```

### Issue Priority

Priority: 2 (default / most bugs should be filed as P2)

### Issue Components

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